Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$121.36	8.329%	$131.4681	$131.47	$131.45	$131.50
Purchase #2	$167.93	9.310%	$183.5643	$183.56	$183.55	$183.60
Purchase #3	$195.79	13.488%	$222.1982	$222.20	$222.20	$222.20
Purchase #4	$223.62	4.716%	$234.1659	$234.17	$234.15	$234.20
Purchase #5	$80.79	11.332%	$89.9451	$89.95	$89.95	$89.90
Purchase #6	$97.45	7.237%	$104.5025	$104.50	$104.50	$104.50
Purchase #7	$44.61	7.752%	$48.0682	$48.07	$48.05	$48.10
7 purchase totals =	$931.55		$1,013.9123	$1,013.92	$1,013.85	$1,014.00